The rigid shell, also known as the housing or casing, of a Helical Bevel Gear Motor is typically made of materials that offer strength, rigidity, and good thermal properties. The choice of material depends on various factors, including the specific application, environmental conditions, and the level of protection required for the internal components. Common materials used for the housing of Helical Bevel Gear Motors include:

1. Cast Iron: Cast iron is a popular choice for gear motor housings due to its excellent strength, durability, and vibration-damping properties. It provides robust protection to the internal gears and components, making it suitable for heavy-duty and industrial applications.

2. Aluminum Alloy: Aluminum alloys are lighter than cast iron and offer good strength-to-weight ratio. They are often used in applications where weight reduction is a consideration, such as in mobile equipment or applications where frequent movement is required.

3. Steel: Steel is another material commonly used for gear motor housings, especially in heavy-duty and industrial settings. It provides high strength and impact resistance, making it suitable for applications where the motor is exposed to harsh conditions or rough handling.

4. Die-Cast Zinc: Die-cast zinc is used in some gear motors, particularly in smaller and lighter-duty models. It offers good strength and can be cost-effective for certain applications.

5. Composite Materials: In some cases, composite materials, such as reinforced plastics or fiberglass, may be used for gear motor housings. These materials offer a balance of strength and lightness and can be suitable for applications where corrosion resistance is essential.

The choice of material for the housing also depends on factors such as cost considerations, specific industry requirements (e.g., food-grade applications), and any regulatory compliance requirements related to material properties. Additionally, proper design considerations, such as ribbing and reinforcement, can enhance the housing's structural integrity and overall performance.